For example, I want to protect my ePub, I encrypt all xhtml files and before Readium load those files, I decrypt it before it loaded. I could decrypt those xhtml files when I need to load some page from spine items of table of content.

The problem is when Readium need to load the epub file, it seems like it need to load the toc.xhtml first, but I don't know where it load the file so I can't decrypt it and I always get the error: "xhtml/toc.xhtml:1: parser error : Start tag expected, '<' not found" and this one: "libc++abi.dylib: terminating with uncaught exception of type ePub3::epub_spec_error: Publications MUST contain exactly one navigation document."

I know that those error above is because the toc.xhtml is encrypt, so that's why I need to know where Readium load or point to toc.xhtml.
Please help.